Please look at Pictures

Kirk T

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Kirk
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Can someone help me identify what I'm pointing at in the picture? I think it has something to do with the TC lockup but I'm not sure The reason I'm investigating this is my '85 K-10 has a noticeable "feel" like it tries to come out of overdrive at highway speeds but then quickly goes away. It has a 700R4. Also, when it's in my driveway and I shift it into neutral to push it it will roll a distance and then "clank" and feel like it shifts into Park. I can rock it and it will be easy to push again.

Also, in the second photo, on the firewall left of the air cleaner, there appears to be solenoid with a plug on the end. What is it for.

Thank you for any help.
 

Kirk T

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Kirk
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I forgot to attach the photos. Here they are
 

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Bextreme04

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Eric
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I forgot to attach the photos. Here they are

The one on the drivers side should be the TCC lockup switch. The one on the passenger side will be a tip-in switch to pull timing from an ESC equipped 305 when you give it some throttle.
 

Kirk T

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Thank you for responding. Is there a way to test the TCC lockup switch? Also, what is ESC that you mentioned? Should I take the plug off and hook a vacuum line back up?

Thank you for helping me.
 

Bextreme04

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Thank you for responding. Is there a way to test the TCC lockup switch? Also, what is ESC that you mentioned? Should I take the plug off and hook a vacuum line back up?

Thank you for helping me.
ESC = Electronic Spark Control.

The 305 was prone to detonation in certain specific situations, so they put an electronic spark control on it to pull timing during certain events to reduce detonation. Lots of people removed the system. A standard HEI distributor will have three wires coming out of the distributor body into the cap. An ESC distributor will have additional wires(I think 4 wires?) coming out of the distributor body and going to the engine wiring harness.

If you have a standard HEI distributor now, then hooking that solenoid up will do nothing. If you still have an ESC distributor, it was likely disconnected because the system wasn't working right and a PO didn't know how to fix it, so they just bypassed the system.

I'm not familiar with the lockup system on these. You can probably look at the electrical schematics to see where everything is supposed to run. My guess would be that the switch is either going bad and that is letting it lock and unlock at cruise, or you have a loose wire somewhere that is making it think you are pressing on the brake.
 

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